DE2411294A1 - PROCESS FOR THE PRODUCTION OF ANHYDRIDES FROM AROMATIC POLYCARBONIC ACIDS - Google Patents

Description

PATENT LAWYERS 2 A 1 1 2 9 A

Dipl.-Ing. P. WIRTH ■ Dr. V. SCHMIED-KOWARZIK Dlpl.-lng. G. DANNENBERG Dr. P. WEINHOLD Dr. D. GUDEL

281T34 6 FRANKFURTAM MAIN

TELEPHONE C0611J

287014 GH. ESCHENHEIMER STRASSE

Case 97
Wd / Sch

LABOFIlTA S.A.

31-53, rue de la Loi

B-1040 Brussels
Belgium

Process for the preparation of anhydrides of aromatic polycarboxylic acids.

409845/1064

The present invention "relates to a method for Manufacture of anhydrides of aromatic polycarboxylic acids.

The anhydrides of aromatic polycarboxylic acids have one wide range of applications, especially in manufacturing of plasticizers, synthetic resins and fibers. The most common are phthalic and pyromellitic anhydrides used. These anhydrides can be produced by vapor phase oxidation of aromatic hydrocarbons from the group: Naphthalene, octahydroanthracene and aromatic hydrocarbons with at least 2 alkyl substituents in the ortho position the general formula:

R ³ -

R ⁴ .-

getting produced,

1 2

wherein R and R are straight or branched chain alkyl groups with about 1-6 carbon atoms and can be the same or different; R ^ and R hydrogen or a Mean alkyl group with about 1-4 carbon atoms and can be the same or different, and in which the total number of carbon atoms of the alkyl aromatic hydrocarbons is no more than about 18.

The vapor phase oxidation of these alkyl aromatic hydrocarbons is generally carried out in the presence of a catalyst composed of yanadium oxide or mixtures of vanadium oxide and various promoters as well as a fire-resistant carrier such as silicon oxide, aluminum oxide, mixtures of silicon oxide and alumina, silicon carbide and the like

409845/1064

consists. However, the desired acid anhydride is obtained in generally along with relatively large amounts of oxidation by-products. The known catalysts generally have unsatisfactory selectivity. In the oxidation of durene or 1,2,4,5-tetramethylbenzene contains the obtained Pyromellitic dianhydride or 1,2,4,5-benzene tetracarboxylic acid edianhydride as by-products trimellitic anhydride, 4,5-dimethylphthalic acid and 4-methylphthalic anhydride. These by-products are formed at the expense of the pyromellitic dianhydride yield, and also make it difficult these byproducts purify the desired dianhydride.

There are previously various proposals for improving the selectivity in the oxidation of the alkyl aromatics to anhydrides been made. Changes in working conditions and / or the addition of additives to the catalyst, however, generally tends to slow the rate of oxidation of the feed or to form combustion products guided. In addition, the yield of anhydrides based on the amount charged has not increased satisfactorily increased.

The object of the present invention is therefore to create an improved method for the vapor phase oxidation of Hydrocarbons as well as the creation of a new, improved Catalyst for the vapor phase oxidation of aromatic Hydrocarbons to the corresponding acid anhydrides with the lowest possible formation of by-products.

The vapor phase oxidation according to the invention includes oxidation of alkyl aromatics of the general formula:

R ³ -

y -

·' H
409845/1064

where R, R, Έτ and R. have the same meaning as in the general formula on page 2 of the description and where the total number of carbon atoms of the alkyl aromatic hydrocarbons is not more than about 18,

in the presence of a catalyst which consists essentially of a support and vanadium oxide which has been applied to the support by hydrolysis of yanadium oxytrihalide and subsequent calcination of the catalyst. The halide of the vanadium oxytrihalide is one of chlorine or bromine, and the oxidation temperature is between about 300 and 55O ⁰ G.

The catalyst according to the invention is prepared by impregnating a fire-resistant support with a liquid oxytrihalide of vanadium, removing excess oxytrihalide, hydrolyzing the oxytrihalide applied to the support and calcining the catalyst, the halide being that of chlorine or bromine. The fire-resistant carrier, which can be used in any conventional form, for example in the form of spheres, bits ^J , cylinders, threads and the like, consists of silicon oxide, aluminum oxide, mixtures of silicon and aluminum oxide, silicon carbide or other such fire-resistant materials. The liquid oxytrihalide of vanadium with which the support is impregnated is prepared by reacting chlorine or bromine with vanadium oxides. Vanadium oxytrichloride is preferably used, and this can also be achieved by reacting thionyl chloride with vanadium

pentoxide according to the reaction scheme: Yp ^ 5 ⁺ ^ SOCl ₂ >

2 VOCl, + 3 SO2 can be produced. During impregnation the vanadium oxytrihalide carrier becomes the presence moisture is preferably avoided and the support should therefore be dried beforehand. According to a preferred embodiment of the present invention, the carrier is disclosed in

^ Pellet

409845/1064

the liquid oxytrihalide of vanadium is immersed, removed again and then the excess of oxytrihalide removed. The immersion time depends on various factors, "for example on the type of carrier, the size and Porosity of the support parts, etc. However, others can also be used Processes such as spraying, vapor phase impregnation and the like, used at atmospheric, positive or negative pressure will.

To hydrolyze the oxytrihalide of vanadium, water, steam, or a carrier gas such as air saturated with water can be used. This hydrolysis is conducted at a temperature of about 0 to 150 ⁰ C, preferably from about 5 to 100 C, in particular from about 10 to 50 ⁰ C is performed. The hydrolysis time depends on many factors such as the temperature and flow rate of the hydrolyzing gas, the particle size of the support and the depth of the catalyst bed. The hydrolysis is preferably carried out by a process in which the carrier particles and the hydrolyzing agent are in intimate contact.

The amount of vanadium oxide used according to the invention on the catalyst can vary widely and depends primarily Line depends on the particle size and porosity of the carrier. Catalysts With a high content of vanadium oxide can be produced by successively several impregnation and Carries out hydrolysis processes, either after each hydrolysis stage or a calcination stage takes place only after the last hydrolysis stage. It is therefore possible to use catalysts to produce about 0.1 to 25 wt .- #, preferably about 1 to 10 wt .- $, vanadium oxide, based on the weight of the finished catalyst, contain *

In addition to vanadium oxide, the catalysts according to the invention can also contain other metal oxides, such as titanium, tin, niobium, germanium, Chromium, phosphorus oxides and the like, which contain as Act promoter. These other metal oxides can be incorporated into the catalyst according to the invention by the catalyst

4098A5 / 106A

treated with a liquid oxytral halide of vanadium " which contains a dissolved halide or other soluble salt of the metal whose oxide is used as a promoter works. According to a preferred embodiment of the invention, the carrier with liquid Yanadium oxytrichloride, which contains dissolved titanium, tin, mob, germanium, chromium or phosphorus chi or id or a mixture of these chlorides, impregnated. Subject to the hydrolysis and calcination stage a catalyst, which Vanadiuraoxyd together with a or contains more promoters. These promoters can also be added to the catalyst before or after the formation of the vanadium oxide be incorporated. For example, the catalyst support can be made with a halide or a salt of the above Metals or with a mixture of these halides and / or salts are impregnated, which are then converted into the corresponding Oxides are converted. The carrier, which the. Or the Contains promoter (s) is then treated with the vanadium oxytrichloride or yanadium oxytribromide and then the product hydrolyzed and calcined. The metal promoters can also be incorporated into the catalyst by other known methods will.

The amount of promoter optionally used in the catalyst depends on the physical properties of the support, the amount of metal halide or metal salt used and the number of treatments. Suitable catalysts can be used can be produced containing up to about 25 wt contain such promoters. In general, however, the promoter level in the catalyst will not be more than about 10 Wt .- $ 6; these percentages relate to weight of the finally obtained catalyst.

It has surprisingly been found that the yield of the desired anhydride is improved if the oxidation in Presence of the catalysts of the invention is carried out. Not just the amount of anhydride, but also the purity this anhydride is higher than when using conventional catalysts under similar operating conditions.

409845/1064

The process according to the invention is suitable for the oxidation of aromatic hydrocarbons such as naphthalene and octahydroanthracene and polyalkylbenzenes with at least 2 alkyl substituents, which can be the same or different, in the ortho position. These polyalkylbenzenes include, for example way 1,2-dimethyl "benzene or ortho-xylene, 1-methyl-2-butylbenzene, 1,2-diisopropylbenzene, 1,2-diethylbenzene ,. 1-methyl-2- (4-methylpentyl) benzene, i-methyl-2-isopropylbenzene, 1-methyl-2-propylbenzene, 1,2,4,5-tetraethylbenzene, 1,2,4,5-tetraisopropylbenzene, 1,2,4,5-tetramethylbenzene or durene and the like. Anhydrides of the corresponding benzene polycarboxylic acids, namely o-phthalic anhydride and pyromellitic dianhydride, obtained by oxidation of the above-mentioned hydrocarbons.

The Dampfphasenoxydationsverfahren according to the invention is generally conducted at temperatures of about 300 - 55O ⁰ G carried out, although other temperatures may be used under certain conditions. The temperature depends primarily on the load. o-xylene, for example, preferably at a temperature of about 325 - 475 ⁰ C oxidized while durene preferably at about 350 - 450 ⁰ C is oxidized. The pressure can also vary, although the oxidation is generally carried out at about atmospheric pressure. The other operating conditions, such as the relative proportions and flow rates of the reactants and other features of the process, are essentially the same as those of the processes generally used for the oxidation of aromatic hydrocarbons to anhydrides of benzene polycarboxylic acids.

The following examples serve to explain the present in more detail Invention, but without limiting it.

409845 / 106A

example 1

A catalyst support (400 mL), which consists essentially of silicon carbide "existed and about 25-3O ^ SiO ₂ contained, and was in the form of beads having an average size of 4.7 mm, 1 hour and calcined at 35O ⁰ C. Man This carrier was placed in a cylindrical Pyrex reaction vessel (diameter: 70 mm, height: 200 mm) with 3 openings at the top and 1 opening at the bottom. Vanadium oxytrichloride was introduced through one of the upper openings Upper openings were used to remove the exhaust gases or to remove the vapors formed during the hydrolysis. The opening at the bottom was used to remove the excess of VOCl ^ and to introduce the hydrolysis agent. The lower part of the reaction vessel contained a bed (depth: 20 mm) of aluminum Raschig rings To remove the moisture, a stream of dry, pure nitrogen was passed over the catalyst support in the for 30 minutes Reaction vessel passed.

Sufficient VOCl (225 ml) was introduced so that the carrier was completely covered by this liquid, at a temperature of 25 ° C. After 15 minutes, the excess VOCl was removed using a stream of nitrogen at the top of the reaction vessel to aid in the removal of the liquid. Then, the VOCl was hydrolyzed for 1 hour by bringing it at a temperature of 25 ⁰ C with a flow of saturated water contacts air, this air being introduced at the bottom of the reaction vessel at a rate of 1200 liters / hour. Then the catalyst is removed from the reaction vessel, calcined by In passing dry air for 16 hours at 15O ⁰ C and then dried for 1 hour at 500 ⁰ C. This catalyst contained 4.9% by weight of vanadium oxide.

409845/1064

A mixture of durol and air containing 0.2 yoI .- # durol was placed in a Pyrex reaction vessel containing a fixed bed of 60 ml of the catalyst prepared in this example. The catalyst, which was in the form of beads, was mixed with Pyrex beads the same size as the catalyst beads. The oxidation was carried out "at 39O ⁰ C and at atmospheric pressure, and 40 g Durol per liter of catalyst per hour were used. This experiment was designated as experiment 1. For comparison, two further, similar experiments, those as experiment 2 and 3 were carried out under the same conditions, but with different catalysts a catalyst was used which contained 6.8% by weight of vanadium oxide, which had been prepared from vanadium oxalate by known processes Contain oxidation products) and determine the purity of the dianhydride (or the amounts of dianhydride in this mixture), and on the basis of these values the yield of pure dianhydride of pyromellitic acid (PMDA) based on the amount charged was calculated.

Yield of crude PMDA content of the yield of pyromellitic acid crude product of pure PMDA dianhydride (wt .- #) (wt .- ^)

Trial 1 87.4 93.4 81.6

Trial 2 81.3 61.3 49.8

Trial 3 74.8 74.0 55.4.

409845 / 1Q 64

Example 2

The procedure described in Example 1 "was essentially followed repeated by adding Durol in the presence of a catalyst in the form of spheres of silicon carbide containing Oxidized 4.9% by weight of vanadium oxide and 0.3% by weight of titanium oxide became. This catalyst was made as described above Vanadium oxytrichloride, which contained titanium tetrachloride dissolved therein. The PMDA yield was "different temperatures as follows:

Temperature C

yield
(Weight to PMDA
- *) 72 , 5 97 , 3 85 , 9

366 380 395

For comparison, the experiment was carried out again in the presence of a Catalyst carried out, the 4.9% by weight of vanadium oxide (produced from ammonium metavanadate) and 0.5% by weight of titanium oxide contained. The highest recovery of PMDA was $ 79.7.

Example 3

The procedure described in Example 1 again essentially followed repeated by adding 1,2,4,5-tetraethylbenzene in the presence of a catalyst in the form of spheres of alpha-alumina ($ 86) and silicon oxide (14? Q, of 4.7 wt .- ^ vanadium oxide and 0.5 5 »chromium oxide, which is composed of vanadium oxytrichloride which contained dissolved chromium oxide was oxidized. The oxidation was carried out at 375 ° C. The yield of pure PMDA was 58.2% by weight.

*) "chromium oxide"

409845/1064

Example 4

The vapor phase oxidation of o-xylene was in the presence a catalyst which was essentially the same as Run 1 of Example 1 except that the final Catalyst 7.1 wt .- ^ contained vanadium oxide. The oxidation conditions were the same as in Example 1 except that the temperature was varied as indicated below.

The yield of phthalic anhydride "was" in the following Oxidation temperatures:

Temperature yield

⁰ O (wt .- ^)

¹ 390. 58.6

410 85.5

425-82.7

435 82.4

445 75.1

For comparison, similar tests were carried out at temperatures between 360 and 490 ^° C. in the presence of a catalyst which contained 7.1% by weight of vanadium oxide which had been produced from ammonium oxalate. The highest yield of phthalic anhydride was 71.9%.

Example 5

Example 2 was essentially repeated except that 1,2,4-trimethyl-5-isopropylbenzene was used as the feed. PMDA was obtained with a selectivity higher than 80 #.

409845/1064

Example 6

A catalyst prepared according to Example 1, the 7.1 wt .- ^ Vanadium oxide was used for the vapor phase oxidation of Naphthalene used at 4-15 ° C. Phthalic anhydride was obtained in a yield of 76 wt .- ^.

Examples 7-9

The vapor phase oxidation of three different aromatic hydrocarbons was carried out in the presence of a catalyst prepared according to Example 1, with the exception that, instead of the oxytrichloride of vanadium, oxytribromide of vanadium was used. The catalyst contained 5 '5 wt -.% Vanadium oxide. The following table shows the oxidation temperature and the selectively obtained anhydride for each charge.

example feed Oxidation
temperature
( ⁰ C) anhydride 7th Octahydroanthracene 420 Pyromellite
acid anhydride d 8th 1-methyl-2-butyl-benzene 410 Phthalic acid
anhydride 9 1,2,4 »5-tetraisopropyl
benzene 390 Pyromellite
acid anhydride example 10

A catalyst according to Example 1 was prepared. However, the catalyst support was first coated with titanium chloride impregnated, hydrolyzed and calcined and then impregnated with vanadium oxytrichloride, hydrolyzed and calcined.

409845/1064

The catalyst contained 5 »25 wt -.% And 0.94 wt Yanadiumoxyd titania.. With this catalyst Durol was oxidized according to the process described in Example 1, but at a temperature of 380 ⁰ G. PMDA was obtained in a yield of
82.4 wt.

409845/1064

Claims (10)

Patent claims: 1. Process for the preparation of anhydrides of benzene polycarboxylic acids by vapor phase oxidation of aromatic Hydrocarbons from the group: naphthalene, octahydroanthracene and polyalkylbenzenes with at least 2 alkyl substituents in ortho-position to each other of the general formula: B ³ E ⁴ 12th
wherein R and R are straight or branched chain alkyl groups with about 1-6 carbon atoms and, R and R are hydrogen or alkyl groups with about 1-4 carbon atoms "and the total number of carbon atoms of the polyalkylbenzenes is not more than about 18, characterized in that the aromatic hydrocarbons at a temperature of about 300 to 55O ⁰ C and in the presence of a catalyst which comprises a fire-resistant support and vanadium oxide and by impregnating the fire-resistant support with an oxytrihalide of the vanadium of chlorine or bromine, hydrolyzing the oxytrihalide from Vanadium and then calcining the catalyst has been produced, can be oxidized. 2. The method according to claim 1, characterized in that as aromatic hydrocarbon naphthalene or o-xylene use amounts to. is used and the temperature is about 325 to 50O ⁰ C 409845/1064 3. The method according to claim 1, characterized in that octahydroanthracene or tetramethylbenzene is used as the aromatic hydrocarbon and the temperature is approximately 300 "to 500 ^° C. · · 4. The method according to claim. 1 - 3 _f, characterized in that vanadium oxytrichloride is used as the oxytrihalide of vanadium. 5. The method according to claim 1-4 »characterized in that in Mixing with the vanadium oxide a metal oxide promoter is used in the catalyst. 6. The method according to claim 5 »characterized in that the metal oxide promoter is a metal oxide of: titanium, Tin, Mob, Germanium, Chromium, Phosphorus or mixtures of this is used. 7. The method according to claim 5-6, characterized in that a catalyst is used in which the metal oxide promoter prior to "impregnating the support with the vanadium oxytri halide has been applied to the fire-resistant support. 8. The method according to claim 5-7 »characterized in that a catalyst is used in which the metal oxide promoter has thereby been applied to the fire-resistant support, that a soluble salt of the metal of the oxytrihalide dissolved from the vanadium and the fire-resistant carrier with the solution is impregnated and then the salts are hydrolyzed to the oxide 9. The method according to claim 1-8, characterized in that a catalyst is used which is about 0.1 to 25 wt .- $, preferably about 1 to 10 wt .- ^, contains vanadium oxide. 10. The method according to claim 5-9, characterized in that a catalyst is used which is about 0.1 to 25 wt .- ^, based on the catalyst, containing a metal oxide promoter. 409845/1064. . ^